U.S. patent number 9,077,906 [Application Number 14/165,587] was granted by the patent office on 2015-07-07 for video contrast adjusting method.
This patent grant is currently assigned to AVER INFORMATION INC.. The grantee listed for this patent is AVer Information Inc.. Invention is credited to Wei-Ting Pong, Cheng-Mou Tsai, Huah Tu.
United States Patent |
9,077,906 |
Tsai , et al. |
July 7, 2015 |
Video contrast adjusting method
Abstract
A method for adjusting a contrast value of a video capturing end
to a optimum contrast value is provided. Firstly, a first video
image and a first contrast value of the first video image are
gathered by a software part. A reference image is generated
according to the first video image. The first video image is
compared with the reference image to generate a first image
evaluation value and an operation is performed to determine whether
the first image evaluation value is greater than a first threshold.
When the first image evaluation value is smaller than the first
threshold, a second contrast value is generated according to the
first contrast value and a dynamical contrast adjusting value. The
second contrast value is sent to a firmware part by the software
part to adjust a contrast value of the video capturing end
according to the second contrast value.
Inventors: |
Tsai; Cheng-Mou (New Taipei,
TW), Pong; Wei-Ting (New Taipei, TW), Tu;
Huah (New Taipei, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
AVer Information Inc. |
New Taipei |
N/A |
TW |
|
|
Assignee: |
AVER INFORMATION INC. (New
Taipei, TW)
|
Family
ID: |
53492122 |
Appl.
No.: |
14/165,587 |
Filed: |
January 28, 2014 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N
5/243 (20130101); H04N 5/235 (20130101); H04N
5/2351 (20130101) |
Current International
Class: |
H04N
5/57 (20060101); H04N 5/14 (20060101); G06K
9/40 (20060101); H04N 5/235 (20060101); H04N
5/243 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Moe; Aung S
Assistant Examiner: Cowan; Euel
Attorney, Agent or Firm: CKC & Partners Co., Ltd.
Claims
What is claimed is:
1. A method for adjusting a contrast value at a video capturing end
to an optimum contrast value, comprising: capturing a first video
image and a first contrast value of the first video image by a
software part; generating a reference image according to the first
video image; comparing the first video image with the reference
image to generate a first image evaluation value; determining
whether the first image evaluation value is greater than a first
threshold; determining a second contrast value according to the
first contrast value and a dynamical contrast adjusting value when
the first image evaluation value is smaller than the first
threshold: sending the second contrast value to a firmware part by
the software part; and adjusting the contrast value the video
capturing end by the firmware part according to the second contrast
value.
2. The method of claim 1, wherein the operation of generating the
reference image according to the first video image further
comprises using a histogram equalization method to process the
first video image to generate the reference image.
3. The method of claim 1, wherein the operation of comparing the
first video image with the reference image to generate the first
image evaluation value further comprises using a structural
similarity (SSIM) evaluation process to compare the first video
image with the reference image to generate the first image
evaluation value.
4. The method of claim 1, wherein the operation of adjusting the
contrast value of the video capturing end further comprises using
the firmware part to adjust a contrast value of aperture of the
video capturing end to the second contrast value.
5. The method of claim 1, wherein when the first image evaluation
value is greater than the first threshold, the first contrast value
is the optimum contrast value.
6. The method of claim 1, wherein the operation of determining the
second contrast value according to the first contrast value and the
dynamical contrast adjusting value further comprises: quantifying
the first contrast value to make the first contrast value be
between 0 and 100; setting the dynamical contrast adjusting value
to a first positive value when the first contrast value is smaller
than or equal to a second threshold; and setting the dynamical
contrast adjusting value to a first negative value when the first
contrast value is greater than a second threshold; wherein the
absolute values of the first positive value and the first negative
are the same; wherein the second contrast value is equal to the
first contrast value plus the dynamical contrast adjusting
value.
7. The method of claim 6, wherein the second threshold is 100-n,
and the first positive value is n, and the first negative value is
-n, wherein n is a nature number.
8. The method of claim 1, further comprising: capturing a second
video image by the video capturing end according to the second
contrast value; comparing the second video image with the reference
image to generate a second image evaluation value; determining
whether the second image evaluation value is greater than the first
threshold; determining whether the second image evaluation value is
greater than the first image evaluation value when the second image
evaluation value is smaller than the first threshold; determining a
third contrast value according to the second contrast value and the
dynamical contrast adjusting value when the second image evaluation
value is greater than the first image evaluation value; determining
whether the third contrast value is between 0 and 100; sending the
third contrast value to the firmware part by the software part when
the third contrast value is between 0 and 100; and adjusting the
contrast value of the video capturing end by the firmware part
according to the third contrast value.
9. The method of claim 8, wherein when the second image evaluation
value is greater than the first threshold, the second contrast
value is the optimum contrast value.
10. The method of claim 8, wherein the operation of comparing the
second video image with the reference image to generate the second
image evaluation value further comprises using a SSIM evaluation
process to compare the second video image with the reference image
to generate the second image evaluation value.
11. The method of claim 8, wherein when the third contrast value is
not between 0 and 100, the second contrast value is the optimum
contrast value.
12. The method of claim 8, wherein the operation of determining the
third contrast value according to the second contrast value and the
dynamical contrast adjusting value further comprises adding the
dynamical contrast adjusting value to the second contrast value to
form the third contrast value.
13. The method of claim 8, wherein when the second image evaluation
value is less than the first image evaluation value, the method
further comprises: determining whether the first contrast value is
between n and (100-n), and whether the dynamical contrast adjusting
value has been multiplied by (-1); determining whether one of image
evaluation values is greater than twice of the first image
evaluation value when the first contrast value is between a and
(100-n) and the dynamical contrast adjusting value has not been
multiplied by (-1); multiplying the dynamical contrast adjusting
value by (-1) when there is no image evaluation values greater than
twice of the first image evaluation value; determining a fourth
contrast value according to the first contrast value and the
dynamical contrast adjusting value that is multiplied by (-1);
sending the fourth contrast value to the firmware part by the
software part; and adjusting the contrast value of the video
capturing end by the firmware part according to the fourth contrast
value.
14. The method of claim 13, further comprising: when the first
contrast value is not located between n and (100-n), setting the
maximum of image evaluation values as an optimum image evaluation
value, and setting a contrast value corresponding to the optimum
image evaluation value as the optimum contrast value.
15. The method of claim 13, further comprising: when the dynamical
contrast adjusting value has been multiplied by (-1), setting the
maximum of image evaluation values as an optimum image evaluation
value, and setting a contrast value corresponding to the optimum
image evaluation value as the optimum contrast value.
16. The method of claim 13, further comprising: setting an image
evaluation value that is greater than twice of the first image
evaluation value as a optimum image evaluation value, and setting a
contrast value corresponding to the optimum image evaluation value
as the optimum contrast value.
17. The method of claim 13, wherein the operation of determining
whether the dynamical contrast adjusting value has been multiplied
by (-1) further comprising: determining whether the first contrast
value has been added by the dynamical contrast adjusting value and
the first contrast value has been subtracted by the dynamical
contrast adjusting value.
18. The method of claim 13, wherein the operation of determining
the fourth contrast value according to the first contrast value and
the dynamical contrast adjusting value that is multiplied by (-1)
further comprises: adding the dynamical contrast adjusting value
that is multiplied by (-1) to the first contrast value to form the
fourth contrast value.
19. The method of claim 13, wherein the operation of determining a
fourth contrast value according to the first contrast value and the
dynamical contrast adjusting value that is multiplied by (-1)
further comprises to add the first contrast value and the dynamical
contrast adjusting value that is multiplied by (-1) to form the
fourth contrast value.
Description
BACKGROUND
1. Field of Invention
The invention relates to an adjusting method, and particularly
relates to a method for adjusting a contrast value of a video
image.
2. Description of Related Art
A contrast value is a property of a video image, defined as the
ratio of the luminance of the brightest color (white) to that of
the darkest color (black) in the video image. A high contrast ratio
is a desired aspect of any display.
Typically, a software adjusting method is used to adjust the
contrast value of a video image to improve display quality.
However, when a video image has a lower contrast ratio, even though
software is used to adjust the contrast value of the video image,
the adjustment result usually cannot meet the requirement because
the content information of the original video image is not enough.
For example, for the darker region in the video image, even though
the software is used to adjust the darker region to have a highest
contrast value, a lot of content information still miss in the
final display result because the original video image data does not
contain these content information. Therefore, another method of
directly adjusting the contrast value of the video capturing end is
provided. However, in such method, the eyes of human are used to
determine the adjustment result of the contrast value. Therefore,
the adjustment result is not always correct. In other words, it is
very difficult to use the above methods to improve the contrast
value.
SUMMARY
Accordingly, the present invention provides a contrast value
adjustment method. A software end is used to determine the image
quality. The determined result is transferred to a firmware end to
adjust the contrast value of the video capturing end. Therefore,
the contrast value of the video capturing end can be dynamically
changed to improve the image quality of the captured video.
An aspect of the invention is to provide a method for adjusting a
contrast value of a video capturing end to an optimum contrast
value. At first, a first video image and a first contrast value of
the first video image are gathered by a software part. A reference
image is generated according to the first video image. The first
video image is compared with the reference image to generate a
first image evaluation value and an operation is performed to
determine whether the first image evaluation value is greater than
a first threshold. When the first image evaluation value is smaller
than the first threshold, a second contrast value is generated
according to the first contrast value and a dynamical contrast
adjusting value. The second contrast value is sent to a firmware
part by the software part to adjust the contrast value of the video
capturing end according to the second contrast value.
In an embodiment, the operation of generating the reference image
according to the first video image further comprises: using a
histogram equalization method to process the first video image to
generate the reference image.
In an embodiment, the operation of comparing the first video image
with the reference image to generate the first image evaluation
value further comprises using a structural similarity (SSIM)
evaluation process to compare the first video image with the
reference image to generate the first image evaluation value.
In an embodiment, the operation of adjusting the contrast value of
the video capturing end further comprises using the firmware part
to adjust a contrast value of aperture of the video capturing end
to the second contrast value.
In an embodiment, when the first image evaluation value is greater
than the first threshold, the first contrast value is the optimum
contrast value.
In an embodiment, the operation of determining the second contrast
value according to the first contrast value and the dynamical
contrast adjusting value further comprises: quantifying the first
contrast value to make the first contrast value be between 0 and
100, setting the dynamical contrast adjusting value to a first
positive value when the first contrast value is not greater than a
second threshold; and setting the dynamical contrast adjusting
value to a first negative value when the first contrast value is
greater than a second threshold. The absolute values of the first
positive value and the first negative are the same. The second
contrast value is equal to the first contrast value plus the
dynamical contrast adjusting value. The second threshold is 100-n,
the first positive value is n and the first negative value is
-n.
In an embodiment, the adjustment method further comprises:
capturing a second video image by the video capturing end according
to the second contrast value; comparing the second video image with
the reference image to generate a second image evaluation value;
determining whether the second image evaluation value is greater
than the first threshold; determining whether the second image
evaluation value is greater than the first image evaluation value
when the second image evaluation value is smaller than the first
threshold; determining a third contrast value according to the
second contrast value and the dynamical contrast adjusting value
when the second image evaluation value is greater than the first
image evaluation value; determining whether the third contrast
value is between 0 and 100; sending the third contrast value to the
firmware part by the software part when the third contrast value is
between 0 and 100; and adjusting the contrast value of the video
capturing end by the firmware part according to the third contrast
value.
In an embodiment, when the second image evaluation value is greater
than the first threshold, the second contrast value is the optimum
contrast value.
In an embodiment, the operation of comparing the second video image
with the reference image to generate the second image evaluation
value further comprises using a SSIM evaluation process to compare
the second video image with the reference image to generate the
second image evaluation value.
In an embodiment, when the third contrast value is not between 0
and 100, the second contrast value is the optimum contrast
value.
In an embodiment, the operation of determining the third contrast
value according to the second contrast value and the dynamical
contrast adjusting value further comprises adding the dynamical
contrast adjusting value to the second contrast value to form the
third contrast value.
In an embodiment, when the second image evaluation value is greater
than the first image evaluation value, the adjustment method
further comprises: determining whether the first contrast value is
between n and (100-n), and the dynamical contrast adjusting value
has been multiplied by (-1); determining whether one of image
evaluation values is greater than twice of the first image
evaluation value when the first contrast value is located between n
and (100-n) and the dynamical contrast adjusting value has not been
multiplied by (-1); multiplying the dynamical contrast adjusting
value by (-1) when there is no image evaluation values greater than
twice of the first image evaluation value; determining a fourth
contrast value according to the first contrast value and the
dynamical contrast adjusting value that is multiplied by (-1);
sending the fourth contrast value to the firmware part by the
software part; and adjusting the contrast value of the video
capturing end by the firmware part according to the fourth contrast
value.
In an embodiment, the method further comprises setting an image
evaluation value with a maximum value as an optimum image
evaluation value and a contrast value corresponding to the optimum
image evaluation value is the optimum contrast value when the first
contrast value is not located between n and (100-n).
In an embodiment, the method further comprises to set an image
evaluation value with a maximum value as an optimum image
evaluation value and a contrast value corresponding to the optimum
image evaluation value is the optimum contrast value when the
dynamical contrast adjusting value has been multiplied by (-1).
In an embodiment, the method further comprises to set an image
evaluation value that is greater than two times of the first image
evaluation value as an optimum image evaluation value and a
contrast value corresponding to the optimum image evaluation value
is the optimum contrast value.
In an embodiment, the operation of determining whether the
dynamical contrast adjusting value has been multiplied by (-1)
further comprises to determine whether the first contrast value has
been added by the dynamical contrast adjusting value and the first
contrast value has been subtracted by the dynamical contrast
adjusting value.
In an embodiment, the operation of determining a fourth contrast
value according to the first contrast value and the dynamical
contrast adjusting value that is multiplied by (-1) further
comprises to add the dynamical contrast adjusting value that is
multiplied by (-1) to the first contrast value to form the fourth
contrast value.
In view of the above, the software part can send the contrast value
to the firmware part. Then, the firmware part can dynamically
adjust a contrast value of the video capturing end according to the
received contrast value to improve the image quality.
It is to be understood that both the foregoing general description
and the following detailed description are by examples, and are
intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be more fully understood by reading the following
detailed description of the embodiment, with reference made to the
accompanying drawings as follows:
FIG. 1 illustrates a schematic diagram showing a contrast value
adjustment in accordance with a preferred embodiment of the
invention;
FIG. 2 illustrates a flow chart for determining a first contrast
value C1 by the software part in accordance with a preferred
embodiment of the invention; and
FIG. 3 illustrates a flow chart for determining the subsequent
contrast value according to the first contrast value C1 by the
software part in accordance with a preferred embodiment of the
invention.
DETAILED DESCRIPTION
Specific embodiments of the invention are described in details as
follows with reference to the accompanying drawings, wherein
throughout the following description and drawings, the same
reference numerals refer to the same or similar elements and are
omitted when the same or similar elements are stated
repeatedly.
FIG. 1 illustrates a schematic diagram to adjust video image
contrast value in accordance with a preferred embodiment of the
invention. A video capturing end 101, a video outputting end 102
and a video processing end 103 are used to adjust a video image
contrast value. The video processing end 103 further comprises a
software part 1031 and a firmware part 1032. Accordingly, the video
capturing end 101 sequentially captures the video image Y0.about.Yn
and send them to the video processing end 103. The video processing
end 103 dynamically adjusts the contrast value of the video
capturing end 101 according to the video image Y0.about.Yn. Then,
the video capturing end 101 captures a next image according to the
adjusted contrast value, and the video outputting end 102 displays
this image. In an embodiment, the video capturing end 101 is a
camera. The video outputting end 102 is a display. When the video
processing end 103 adjusts the contrast value of the video
capturing end 101, the video processing end 103 collects an initial
video image (referred to as a video image Y0) captured by the video
capturing end 101. Then, the video processing end 103 determines
the initial contrast value C0 of the video image Y0 according to
the contrast value of the video capturing end 101 used to capture
the video image Y0. The software part 1031 determines a desired
contrast value (referred to as a first contrast value C1) according
to the initial contrast value C0 of the video image Y0. Then, the
first contrast value C1 is sent to the firmware part 1032. The
firmware part 1032 adjusts the contrast value of the video
capturing end 101 according to the first contrast value C1. In an
embodiment, the operation of adjusting the contrast value of the
video capturing end fis to adjust a contrast value of aperture of
the video capturing end to the first contrast value C1. The video
capturing end 101 captures another next image (video image Y1)
according to the adjusted contrast value. Then, the image quality
of the video image Y0 is compared with that of the video image Y1
by the software part 1031 so as to determine another desired
contrast value (referred to as a second contrast value C2). The
second contrast value C2 is sent to the firmware part 1032. The
firmware part 1032 adjusts the contrast value of the video
capturing end 101 according to the second contrast value C2. In an
embodiment, the operation of adjusting the contrast value of the
video capturing end fis to adjust a contrast value of aperture of
the video capturing end to the second contrast value C2. The video
capturing end 101 captures another next image (video image Y2)
according to the adjusted contrast value. Then, the image quality
of the video image Y1 is compared with that of the video image Y2
by the software part 1031 so as to determine another desired
contrast value (referred to as a third contrast value C3). The
third contrast value C3 is sent to the firmware part 1032. The
firmware part 1032 adjusts the contrast value of the video
capturing end 101 according to the third contrast value C3. In an
embodiment, the operation of adjusting the contrast value of the
video capturing end fis to adjust a contrast value of aperture of
the video capturing end to the third contrast value C3. The video
capturing end 101 captures another next image (a video image Y3)
according to the adjusted contrast value. Then, the image quality
of the video image Y2 is compared with that of the video image Y3
by the software part 1031 to determine another desired contrast
value (a fourth contrast value C4). The rest of the operations may
be deduced by analogy. The above process is repeated until the
image quality of the video image matches a threshold image quality.
At this time, the contrast value is defined as the optimum contrast
value.
FIG. 2 illustrates a flow chart to determine the first contrast
value C1 by the software part in accordance with a preferred
embodiment of the invention. Please refer to FIG. 1 and FIG. 2. In
operation 201, the initial video image Y0 and its corresponding
contrast value C0 are gathered. In an embodiment, the video
processing end 103 collects the initial video image Y0 and the
corresponding contrast value C0 gathered by the video capturing end
101. The initial video image Y0 is used to generate a reference
image X. The contrast value C0 is used to determine a dynamical
contrast adjusting value .DELTA.C.
In operation 202, a reference image X is generated. In an
embodiment, a histogram equalization method is used to process the
initial video image Y0 to generate an image with better visual
quality. This image is referred to as a reference image X. The
image quality of the reference image X is used as the required
image quality displayed by the video outputting end 102. The
histogram equalization method is a technique for adjusting image
intensities to enhance contrast. In an embodiment, the Histogram
equalization method provided by T. Arici is used. A typical image
contains millions of data points, called pixels. The histogram
equalization method measures and equalizes each pixel's
luminescence. By rearranging the pixels' luminescence, the contrast
value of an image is improved.
In operation 203, a structural similarity (SSIM) evaluation process
is performed to generate an image evaluation value Q0. The SSIM
evaluation process is used to compare the luminescence l(x, y),
contrast c(x, y) and structural s(x, y) of two video images. The
structural similarity value is defined as follows.
SSIM(x,y)=[l(x,y)].sup..alpha.[c(x,y)].sup..beta.[s(x,y)].sup..gamma.
The maximum value of the structural similarity value is 1.
Accordingly, the image evaluation value Q0 between the initial
video image Y0 and the reference image X is calculated by the
structural similarity evaluation process. The greater the image
evaluation value Q0 is, the higher of the similarity between the
initial video image Y0 and the reference image X is. That is, the
image quality of the initial video image Y0 is similar to that of
the reference image X. Therefore, in operation 204, a determination
process is performed to determine whether the image evaluation
value Q0 is greater than a threshold value, such as 0.95. When the
image evaluation value Q0 is greater than 0.95, the image quality
of the initial video image Y0 is similar to that of the reference
image X. That is, the image quality of the initial video image Y0
matches the required image quality. Therefore, it is not necessary
to adjust the contrast value of the video capturing end 101 again.
The contrast adjustment process is ended.
In contrast, when the image evaluation value Q0 is smaller than
0.95, the image quality of the initial video image Y0 is not
similar to that of the reference image X. That is, the image
quality of the initial video image Y0 does not match the required
image quality. Therefore, it is necessary to adjust the contrast
value of the video capturing end 101 again. At this time, operation
205 is performed to determine the dynamical contrast adjusting
value .DELTA.C according to the contrast value C0. In an
embodiment, the contrast value is quantified for convenience. The
quantified contrast value is between 0 and 100. Accordingly, when
the contrast value C0 of the initial video image Y0 is not greater
than 95, the dynamical contrast adjusting value .DELTA.C is set to
a first positive value, such as 5. In contrast, when the contrast
value C0 of the initial video image Y0 is greater than 95, the
dynamical contrast adjusting value .DELTA.C is set to a first
negative value, such as -5. That is, the absolute value of the
first positive value and that of the first negative value are the
same. It is noted that the above embodiment does not intend to
limit the dynamical contrast adjusting value .DELTA.C. On the other
hand, the contrast value C0 of the initial video image Y0 is not
greater than 95. That is, when the dynamical contrast adjusting
value .DELTA.C is added to the contrast value C0 to form the first
contrast value C1, the first contrast value C1 is still smaller
than 100. Therefore, the dynamical contrast adjusting value
.DELTA.C is set to 5. In contrast, the contrast value C0 of the
initial video image Y0 is greater than 95. That is, when the
dynamical contrast adjusting value .DELTA.C is added to the
contrast value C0 to form the first contrast value C1, the first
contrast value C1 is greater than 100. Therefore, the dynamical
contrast adjusting value .DELTA.C is set to -5.
In operation 206, the first contrast value C1 is determined. In an
embodiment, the first contrast value C1 is equal to the contrast
value C0 plus the dynamical contrast adjusting value .DELTA.C,
C1=C0+.DELTA.C. Accordingly, the software part 1031 is responsible
for to perform the operation 201 to the operation 206 to determine
the first contrast value C1 according to the initial contrast value
C0 of the video image Y0 when the image evaluation value Q0 between
the initial video image Y0 and the reference image X is smaller
than 0.95. Then, the first contrast value C1 is sent to the
firmware part 1032 to set the contrast value. That is, the software
part 1031 controls the firmware part 1032 to set the first contrast
value C1 as it's contrast value in operation 207. Then, the first
contrast value C1 is used to determine the following contrast
value.
FIG. 3 illustrates a flow chart to determine the following contrast
value according to the first contrast value C1 by the software part
in accordance with a preferred embodiment of the invention. In
operation 301, a new image Yi with the first contrast value C1 is
gathered. In an embodiment, the video processing end 103 collects
the first video image Y1 that is gathered by the video capturing
end 101 with a contrast value adjusted according to the first
contrast value C1.
In operation 302, a structural similarity (SSIM) evaluation process
is performed to generate an image evaluation value Qi. The image
evaluation value Qi between the video image Yi and the reference
image X is calculated by the structural similarity evaluation
process. That is, the image quality of the video image Yi is
compared to that of the reference image X to determine the image
evaluation value Qi.
Next, in operation 303, a determination process is performed to
determine whether the image evaluation value Qi is greater than a
threshold value, such as 0.95. When the image evaluation value Qi
is greater than 0.95, the image quality of the video image Yi is
very similar to that of the reference image X. That is, the image
quality of the video image Yi matches the required image quality.
Therefore, the adjusting contrast process is ended. In contrast,
when the image evaluation value Qi is smaller than 0.95, the image
quality of the video image Yi is not similar to that of the
reference image X. That is, the image quality of the video image Yi
does not match the required image quality. At this time, operation
304 is performed to determine whether the present image evaluation
value Qi is greater than the previous image evaluation value Qi-1.
When the present image evaluation value Qi is greater than the
previous image evaluation value Qi-1, that is, the image quality is
improved after the contrast value is adjusted by the dynamical
contrast adjusting value IC, the adjusting direction is kept. Then,
in operation 305, the contrast value Ci+1 is determined. In an
embodiment, the contrast value Ci+1 is equal to the contrast value
Ci plus the dynamical contrast adjusting value .DELTA.C,
Ci+1=Ci+.DELTA.C. That is, if the contrast value Ci+1 is the second
contrast value C2, the second contrast value C2 is equal to the
first contrast value C1 plus the dynamical contrast adjusting value
.DELTA.C, C2=C1+.DELTA.C.
In operation 306, a determination process is performed to determine
whether the contrast value Ci+1 is located between 0 and 100.
Because the range of the contrast value is set between 0 and 100,
when the contrast value Ci+1 is not located between 0 and 100,
which means the contrast value Ci+1 is wrong, the adjusting
contrast value process is ended. At this time, the optimum contrast
value is the contrast value Ci. In an embodiment, when the contrast
value C2 is not located between 0 and 100, which means the contrast
value C2 is wrong, the adjusting contrast value process is ended.
At this time, the optimum contrast value is the contrast value C1.
Accordingly, the software part 1031 is responsible for to perform
the operation 301 to the operation 306 to determine the contrast
value Ci+1. Then, the contrast value Ci+1 is sent to the firmware
part 1032 to set the contrast value in operation 307. That is, the
software part 1031 controls the firmware part 1032 to set the
contrast value Ci+1 as its contrast value. Then, the firmware part
1032 adjusts the contrast value of the video capturing end 101
according to the contrast value Ci+1. Then, the above operations
are performed again until an optimum contrast value is found.
On the other hand, in operation 304, when the present image
evaluation value Qi is not greater than the previous image
evaluation value Qi-1, that is, the image quality is not improved
after the contrast value is adjusted by the dynamical contrast
adjusting value .DELTA.C, the adjusting direction is not correct.
Therefore, the dynamical contrast adjusting value .DELTA.C is
multiplied by -1 to cooperate with the contrast value C0 to
determine the new contrast value. That the adjusting direction is
reversed. In an embodiment, the captured video image is the video
image Y1. The image quality of the video image Y1 is compared with
that of the reference image X to generate the image evaluation
value Q1. The image quality of the video image Y0 is compared with
that of the reference image X to generate the image evaluation
value Q0. Accordingly, operation 304 is used to determine whether
the image evaluation value Q1 is greater than the image evaluation
value Q0. When the image evaluation value Q1 is greater than the
image evaluation value Q0 that is, compared with the image quality
of the video image Y0, the image quality of the video image Y1 is
more similar to the image quality of the reference image X, and
using the dynamical contrast adjusting value .DELTA.C to adjust the
contrast value may improve the image quality. In contrast, when the
image evaluation value Q1 is smaller than the image evaluation
value Q0, that is, compared with the image quality of the video
image Y1, the image quality of the video image Y0 is more similar
to the image quality of the reference image X, and using the
dynamical contrast adjusting value .DELTA.C to adjust the contrast
value may not improve the image quality. At this time, the
dynamical contrast adjusting value .DELTA.C is multiplied by -1 to
cooperate with the contrast value C0 to determine the new contrast
value.
Because it is not necessary to evaluate the contrast value that has
been evaluated, the new contrast value is calculated according to
the contrast value C0 of the video image Y0. On the other hand, in
operation 308, a determination process is performed to determine
whether the contrast value C0 is between n and (100-n) to prevent
the adjusted contrast value from being out of the range between 0
and 100, and in operation 309, to determine whether the dynamical
contrast adjusting value .DELTA.C has been multiplied by -1 to
prevent the same adjusting process from being performed repeatedly.
In this embodiment, n is a natural number, for example, n is equal
to 5. However, n is not limited to be equal to 5. When the contrast
value C0 of the video image Y0 is greater than 95, the first
contrast value C1 is greater than 100 when the dynamical contrast
adjusting value .DELTA.C is added to the contrast value C0 to form
the first contrast value C1. In contrast, because the first
contrast value C1 is equal to the contrast value C0 minus the
dynamical contrast adjusting value, the first contrast value C1
will be smaller than 0 if the contrast value C0 of the video image
Y0 is smaller than 5. Therefore, the contrast value C0 is limited
to be between 5 and 95. Accordingly, when the contrast value C0 is
out of the range between n and (100-n) in operation 308, the
adjusting process is ended. At this time, the contrast value
corresponding to a maximum image evaluation value the optimum
contrast value. On the other hand, when the contrast value C0 is in
the range between n and (100-n) in operation 308, the operation 309
is performed to determine whether the dynamical contrast adjusting
value .DELTA.C has been multiplied by -1 to prevent the same
adjusting process from being performed repeatedly. When the
dynamical contrast adjusting value .DELTA.C has been multiplied by
-1, the adjusting process is ended. At this time, the contrast
value corresponding to a maximum image evaluation value is the
optimum contrast value.
In contrast, when the contrast value C0 is in the range between n
and (100-n) in operation 308 and the dynamical contrast adjusting
value .DELTA.C has not been multiplied by -1 in operation 309,
operation 310 is performed to determine whether the optimum image
evaluation value Qoptimum is greater than two times of the image
evaluation value Q0. Because when the optimum image evaluation
value Qoptimum is greater than two times of the image evaluation
value Q0, the image quality has been improved much. At this time,
the adjusting process is ended. The contrast value corresponding to
the optimum image evaluation value Qoptimum is used to adjust the
contrast value of the video capturing end 101.
In contrast, when the optimum image evaluation value Qoptimum is
not greater than two times of the image evaluation value Q0, the
dynamical contrast adjusting value .DELTA.C is multiplied by -1 to
cooperate with the contrast value C0 to determine the new contrast
value Ci+1 in the operation 311, Ci+1=C0+.DELTA.C. Then, the
contrast value Ci+1 is sent to the firmware part 1032 to set the
contrast value in operation 312. That is, the software part 1031
controls the firmware part 1032 to set the contrast value Ci+1 as
its contrast value. Then, the firmware part 1032 adjusts the
contrast value of the video capturing end 101 according to the
contrast value Ci+1. Then, the operation 301 is performed again to
capture the video image captured by the video capturing end 101
according to the contrast value Ci+1. Then, the above operations
are performed again until an optimum contrast value is found.
Accordingly, the software part can send the contrast value to the
firmware part. Then, the firmware part can dynamically adjust a
contrast value of the video capturing end according to the received
contrast value to improve the image quality.
Although the invention has been disclosed with reference to the
above embodiments, these embodiments are not intended to limit the
invention. It will be apparent to those of skills in the art that
various modifications and variations can be made without departing
from the spirit and scope of the invention. Therefore, the scope of
the invention shall be defined by the appended claims.
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